jfa journal

AND option

OR option

FRAILTY IN CHILE: DEVELOPMENT OF A FRAILTY INDEX SCORE USING THE CHILEAN NATIONAL HEALTH SURVEY 2016-2017

 

F. Diaz-Toro1,12, F. Petermann-Rocha2,3, N. Lynskey3, G. Nazar4, I. Cigarroa5, C. Troncoso6, Y. Concha-Cisternas7,8, A.M. Leiva-Ordoñez9, M.A. Martinez-Sanguinetti10, S. Parra-Soto3,13, C. Celis-Morales3,11

 

1. Department of Epidemiology, Mailman School of Public Health, Columbia University, New York, New York, USA; 2. Centro de Investigación Biomédica, Facultad de Medicina, Universidad Diego Portales, Santiago, Chile; 3. BHF Glasgow Cardiovascular Research Centre, School of Cardiovascular and Medical Health, University of Glasgow, UK;
4. Departamento de Psicología y Centro de Vida Saludable, Universidad de Concepción, Concepción, Chile; 5. Escuela de Kinesiología, Facultad de Salud, Universidad Santo Tomás, Los Ángeles, 4440000, Chile; 6. Centro de Investigación en Educación y Desarrollo (CIEDE-UCSC), Departamento de Salud Pública, Facultad de Medicina, Universidad Católica de la Santísima Concepción, Concepción, Chile; 7. Escuela de Kinesiología, Facultad de Salud, Universidad Santo Tomás, Talca, Chile; 8. Pedagogía en Educación Física, Facultad de Educación, Universidad Autónoma de Chile, Talca, Chile; 9. Instituto de Anatomía, Histología y Patología, Facultad de Medicina, Universidad Austral de Chile, Valdivia, Chile; 10. Instituto de Farmacia, Facultad de Ciencias, Universidad Austral de Chile, Valdivia, Chile; 11. Human Performance Lab, Education, Physical Activity and Health Research Unit, University Católica del Maule, Talca, Chile; 12. Universidad Andrés Bello, Facultad de Enfermería, Santiago, Chile; 13. Department of Nutrition and Public Health, Universidad del Bío-Bío, Chillan 3780000, Chile

Corresponding Author: Fanny Petermann-Rocha, Ph.D, Centro de Investigación Biomédica, Facultad de Medicina, Universidad Diego Portales, Santiago, Chile, Email: fanny.petermann@udp.cl, Phone number: +56 2 26768968

J Frailty Aging 2023;in press
Published online January 18, 2023, http://dx.doi.org/10.14283/jfa.2023.2

 


Abstract

Background: The Frailty Index (FI) is used to quantify and summarize vulnerability status in people. In Chile, no development and assessment of a FI have been explored.
Objective: To develop and evaluate a FI using representative data from Chilean adults aged 40 years and older stratified by sex.
Design: Cross-sectional study.
Setting: National representative data from the Chilean National Health Survey 2016–2017 (CNHS 2016-2017).
Participants: 3,036 participants older than 40 years with complete data for all variables.
Measurements: A 49-item FI was developed and evaluated. This FI included deficits from comorbidities, functional limitations, mental health status, physical activity, anthropometry, medications, and falls. A score between 0 and 1 was calculated for each person. Descriptive statistics and linear regression models were employed to evaluate the FI’s performance in the population. Comparative analyses were carried out to evaluate the FI score by age (<60 and > 60 years).
Results: The mean FI score was 0.15 (SD:0.09), with a 99% upper limit of 0.46. Scores were greater in women than men (0.17 [SD:0.09]) vs. 0.12 [0.08]); in people older than 80 years (0.22 [0.11]), and in people with ≤8 years of education (0.18 [0.10]) compared with those with >12 years (0.12 [0.08]). The average age-related increase in the FI was 2.3%. When a cut-off point > 0.25 was applied, the prevalence of frail individuals was 11.8% (95% CI: 10.0 to 13.8) in the general population. The prevalence was higher in women 15.9% [95% CI: 13.3 to 18.9] than men 7.4% [95% CI: 5.3 to 10.1]. In a comparative analysis by age, higher FI mean scores and prevalence of frail were observed in people > 60 than younger than 60.
Conclusions: The mean FI score and frailty prevalence were higher in women than men, in people with fewer years of formal education, and incremented markedly with age. This FI can be used for early detection of frailty status focusing on women and middle-aged people as a strategy to delay or prevent frailty-related consequences.

Key words: Frail elderly, frailty, aging.


 

 

Introduction

Frailty is usually associated with aging (1). In fact, the prevalence of frailty varied between 7% to 24% in individuals older than 60 years across the globe (2). Frail people have a higher risk of falls, disability, long-term care and death (3). Therefore, prevention and early detection have become significant challenges for public health and clinical practice (3, 4).
Different measurements/tools have been proposed for frailty assessment (5). Among them, the Frailty Index (FI) (deficit accumulation approach) – proposed by Mitnitski and Rockwood (6) – is recognized due to its ability to identify people at higher risk of adverse health outcomes and mortality (7).
In most studies, the prevalence of frailty has been higher in women than men (8). These differences remain unexplainable; however, they may be associated with social, behavioral, and biological factors (9). To what extent these differences applied to the Chilean population is still unknown.
Although frailty is often associated with older people (because it is a condition that comprises age-related changes due to the lifelong accumulation and exposition of cellular and molecular damage (10, 11)), recent studies have highlighted that frailty may also be present in middle-aged individuals (12, 13).
Population aging worldwide is rapidly accelerating, and Chile is not the exception. In fact, Chile is the only Latin American country that projects for 2050 to have more than 30% of its population aged 60 and over, estimating an increase in older adults over 109%, exceeding the 74.7% projected for the world population (14–16). Moreover, the prevalence of conditions usually associated with aging, such as non-communicable diseases, unhealthy behaviors and habits, as well as other disabilities, have increased in people younger than 60 years in the country (14).
In Chile, no assessment of frailty using a FI has been investigated. Nevertheless, two studies have estimated the prevalence of frailty status in older adults using the frailty phenotype (17, 18). The ALEXANDROS study (18) – which included 2,098 older adults from Santiago – reported that 63.8% and 13.9% of older adults were pre-frail and frail, respectively. In the same line, Troncoso-Pantoja et al. (17) estimated a prevalence of 10.9% for frail and 59% for pre-frail in 233 individuals aged ≥60 from Santiago using data from the Chilean National Health Survey 2016 2017 (CNHS 2016-2017). However, both studies used the frailty phenotype instead of the FI; in the former, the population was not representative of the Chilean population.
Therefore, the FI distribution and the differences by sex remain to be determined in Chilean adults. Considering the existing gaps, this aimed to develop and evaluate a FI using representative data from Chilean adults aged 40 years and older and stratified by sex.

 

Material and methods

Study design

This cross-sectional study uses data from the CNHS 2016–2017. The CNHS is a large, nationally representative population-based study that gathers data on biological and lifestyle risk factors, diet, and health status conducted every six years in urban and rural zones of Chile. To date, this is the latest version of the CNHS available for the country. More information about each survey can be found elsewhere (19). For the current study, 3036 out of 6233 participants older than 40 years and with full data available were included. To weight the sample at the national level, expansion factors suggested by the CNHS 2016–2017 were applied, resulting in an expanded sample of 6,572,447 individuals. All participants provided written consent before participation.
The CNHS 2016–2017 was funded by the Chilean Ministry of Health and approved by the Ethics Research Committee of the School of Medicine at the Pontificia Universidad Católica de Chile (No. 16–019) (19).

Frailty index development

The FI was operationalized as a collection of symptoms, health behaviors, clinical signs, diseases, psychosocial risk factors, cognitive impairments, and functional limitations (20). The original FI method was described using 70 deficits from the Canadian Study of Health Aging. Fortunately, one of the original index’s main characteristics is the capacity to be adapted to the deficits available in different datasets (21). To be considered a deficit, a variable must satisfy the following criteria: i) their prevalence should increase with age; ii) be associated with health status; iii) not saturate too early or have a very low prevalence (22).
For this study, a 49-items frailty index was developed. Standard procedures described by Searle et al. (22) were followed for its construction. Details of the variables included are shown in Table 1. Briefly, the FI included 49 health deficits, and it was evaluated in people aged 40 and older. The included variables – taken from the CNHS 2016-2017 questionaries – were self-reported chronic conditions: Acute Myocardial Infarction, Stroke, Peripheral Venous Disease, Cataracts, Glaucoma, High blood pressure, Diabetes, High Cholesterol, Osteoporosis, Kidney Failure, Chronic Bronchitis/COPD, Arthritis, Knee osteoarthritis, Hip osteoarthritis, Liver Failure, Gallbladder cancer, Gastric cancer, Colon cancer, Thyroid cancer, other cancer. Functional limitations (13 items related to difficulty performing activities of daily living), self-report of mental health (feeling down, depressed, or hopeless, suspected depression and trouble sleeping), self-report of health and status (9 questions related to self-rated health, and perception of self-health), physical activity (assessed by the Global Physical Activity Questionnaire), anthropometry (Body Mass Index), and others (falls in the last years, number of prescribed medication).
In this study, all deficits were scored between 0 and 1, where 0 indicates the absence of the deficit and 1 the presence of a deficit. The variables were dichotomized, and then the number of deficits present was divided by the total number of assessed variables. In addition, when an intermediate category was identified, this was categorized as 0.5. A frailty score was calculated for each participant by dividing the sum of the health deficit scores by the total number of health deficits assessed. This resulted in a score between 0 (no deficits present) and 1 (all deficits present). In addition, a cut-off point of 0.25 was applied to the FI score to estimate the prevalence of frail individuals and to compare with previous Chilean studies.

Table 1. Questionnaire items from the Chilean National Health Survey 2016-2017 to compose a modified version of the Frailty Index

 

Sociodemographic variables

Self-reported data for sociodemographic characteristics, including age, sex, education, and place of residency, were collected from all participants using questionnaires previously validated for the CNHS 2016–2017. The following categories were derived for the sociodemographic variables: age (40-49, 50-59, 60-69, 70-79, and >80 years), sex (men and women), years of education (≤8 years, 9-12 years, and >12 years), and area of residence (urban and rural setting).

Statistical analyses

The distribution of the FI was assessed using a histogram stratified by sex. Descriptive statistics using the FI score as a continuous variable were calculated for the total population and stratified by sex. In addition, frailty mean scores and prevalence for FI-score were reported by sociodemographic characteristics (for the whole population and by sex), including age, education, and place of residency (rural or urban). Comparative analyses by age groups (<60 and ≥60 years) were carried out to estimate differences between middle-aged and older people. Finally, a linear regression analysis was performed to estimate the association of the FI score with age-stratified by sex.
All statistical analyses were conducted using STATA V17 software and survey weights provided by the CNHS 2016–2017 (StataCorp; College Station, TX).

 

Results

3,036 (74.7%) out of 4,063 participants older than 40 years had complete data for all the variables and were, therefore, included in the analysis. Figure 1 shows the distribution of the FI stratified by sex, which was skewed to the right.

Figure 1. Distribution of Frailty Index by Sex

 

The distribution of the FI score, stratified by sex and according to sociodemographic characteristics, is shown in Table 2. Briefly, in the general population, the mean FI score was 0.15 (SD=0.09), with a median of 0.13, ranging from 0 to 0.56, and a 99% upper limit of 0.46. Mean FI scores were greater in people aged 80 and older (0.22 [0.11], and in people with ≤8 years of education (0.18 [0.10]) compared with those with >12 years (0.12 [0.08]).

Table 2. Sociodemographic characteristic of people 40 years and older by Frailty Index Score (49-items) and Frailty Status (score >0.25) (N=3,036: expanded sample=6,572,448)

Continuous variables are expressed as mean and standard deviation (SD). Categorical variables as percentages with their 95% confidence intervals (95%CI).

 

In terms of differences by sex, mean FI scores were greater in women than men (0.17 [0.09] vs. 0.12 [0.08]), and the prevalence of frail individuals was higher in women as well (15.9% [95% CI: 13.3-18.9] vs (7.4 [95% CI: 5.3-10.1]). The same patterns were observed for age and level of education.
Table 2 shows the prevalence of frail individuals when a cut-off points of ≥0.25 was applied. In the general population, the prevalence of frail individuals was 11.8% (95% CI: 10.0-13.8), which was higher in older people with less formal education. No differences were observed according to the area of residence.
Comparative analyses by age groups (<60 and >60 years) are shown in Table 3. Higher FI scores were observed in the group of people > 60 years old than in their counterparts (mean 0.17 [0.10] vs. 0.12 [0.08]). Similarly, a higher prevalence of frail individuals was identified in people aged >60 (20.1% [95% CI: 16.7-23.8] vs. 6.5% [95% CI: 4.8-8.8]).
The average FI score increments with age by sex. The average age-related increase in the FI was 2.3%, and it was higher in women than men. (Figure 2).

Table 3. Sociodemographic characteristics of individuals by Frailty Score and Frailty prevalence stratified by age (<60 and >60 years old)

Continuous variables are expressed as mean and standard deviation (SD). Categorical variables as percentages with their 95% confidence intervals (95% CI).

Figure 2. Average Frailty Index Score 49-items by Sex and Age

Data presented as Frailty Index score by age in men and women. The gray area represented the 95% confidence intervals.

 

Discussion

Following a standard procedure, a 49-items frailty index was developed using Chilean data. This is the first FI developed from a nationally representative population and the first study assessing the distribution of the FI score in the population aged 40 and older in Chile. Therefore, this Chilean-FI may be used as a reference for future studies to evaluate frailty and identify individuals that may be at higher risk in Chile.

Our results showed that FI scores were higher in women, older people, and those with lower educational levels. The mean FI score was 0.15 (0.09) with an average deficit accumulation rate of 0.023. The FI highest value was 0.53, which is significantly lower than 0.7 (the highest value) suggested by previous studies (21, 23).
Compared to our study, lower FI scores for the general population were reported by Williams in the UK (24). In this study, (using a FI-49 items in more than 500,000 adults), the mean FI score was 0.12 (SD=0.07), with a 99th centile of 0.35. However, in age-stratified analyses, similar results to ours were reported by the authors. The mean FI for people under 50 years old was 0.12 (SD=0.08) and 0.11 (SD=0.07) for individuals between 50 and 60 years old. In our population, the mean FI for people aged between 50 and 59 was 0.14 (SD=0.08) and 0.10 (SD=0.06) for those between 40 and 49 years old.
Conversely, higher mean FI scores, but lower maximum and 99th percentile scores, were reported for Khadka et al. in Australia (25). The mean score was 0.20 (SD=0.07), with a maximum of 0.4 and a 99th percentile of 0.36. The population in this study was aged 65 and older, which may explain the high mean score compared to our results.
In terms of differences by sex, higher scores were reported by Hoogendijk et al. (26) in Amsterdam. Using a nationally representative sample of 2,218 individuals aged between 57-88, reported a mean FI score (32-items) of 0.19 (SD=0.12) for the general population, with a 99th centile of 0.53. Similar to our findings, the mean scores were greater in women than in men 0.20 [SD=0.13] and 0.17 [SD=0.11], respectively); however, the authors reported a higher average age-related increase in the FI score than our study (3.5% vs 2.3% per year).
In Chile, no frailty assessments were previously reported using a FI. The ALEXANDROS study (18) – a prospective cohort of individuals older than 60 years old – identified the prevalence of frailty in people aged 60 years and older using the Fried phenotype (18). In this study, the prevalence of frail individuals was 13.9%. In the same line, also using the Fried phenotype, Troncoso-Pantoja et al. (17) estimated a prevalence of 10.9% of frailty in 233 individuals aged ≥60 from Santiago de Chile. To obtain a comparison with these reports, a cut-off point of ≥25 was applied to the Chilean-FI. Our results estimated a higher frail prevalence in ≥60 compared with both previous studies (20.1% for people aged ≥60). Usually, the prevalence of frail individuals is higher using the FI instead of the frailty phenotype (27). The latter may be explained because the FI represents risk profiles of classified conditions accumulated over time, while the frailty phenotype captures signs and symptoms that help differentiate between frailty and disability (27).
Our results partially agree with those published in previous systematic review regarding the prevalence of frailty (28). A recent systematic review and meta-analysis (2021) – that included 62 countries, 240 studies, and more than 1,700,000 participants – estimated that pre-frail and frail prevalence was 45% and 24%, respectively, using FI.
In South America, no previous reports evaluating the prevalence of frailty using a FI were found (the most similar instrument used was the Tilburg Frailty Indicator (TFI)) (29). Yet, a systematic review (29) estimated the prevalence of frailty in 7 south American countries using other instruments (e.g., FRAIL, Fried Phenotype and TFI). In their systematic review, Coelho-Junior et al. identified a higher prevalence of frailty than in our study (29). For instance, 31,2% in Ecuador, 26.1% in Brazil and 19.9% in Peru. In contrast, Colombia (10.6%) and Venezuela (12.4%) had a lower prevalence of frail individuals, more comparable to the figures that we identified using the CNHS 2016-2017 in this study. These differences may be attributable to the variety of methods for assessing frailty, but also to differences in the population composition in terms of age distribution, cultural aspects, and each country’s health system.
Finally, in our study, the mean FI score and the prevalence of frail were higher in women, in people with fewer years of formal education and increased markedly with age. These results are similar to those published in a previous study (30), which reported that the prevalence of frailty was higher in older people, and in socially-economically disadvantaged women (30).

Strengths and Limitations

Among the strengths of this study is the use of representative data from the Chilean population. Moreover, many questionaries and validated scales in the country were used to build the Chilean-FI, which allows for covering different health domains. The instrument developed followed the standard procedures described in the literature, and its performance was in line with previous reports. The Chilean FI may be flexible regarding the number of deficits to include; therefore, this FI may be adjustable according to the research question being addressed.
Yet, this research is not exempt from limitations. Among them, some variables, such as comorbidities and functional limitations, were self-reported. The latter could underestimate the values reported in this study. Finally, we consider that another important limitation in our study is the absence of physical measures such as muscular strength. Many FI’s incorporate this measure as a potential deficit, and the lack of it could have underestimated our prevalence of frailty in all its categories.

 

Conclusion

In conclusion, the FI score and the frailty prevalence were higher in women than men, in people with fewer years of formal education, and incremented markedly with age. We suggest that this FI can be used for early detection of frailty status focusing on women and middle-aged people as a strategy to delay or prevent frailty-related consequences. Finally, this FI may be used as a reference for future studies to understand the complications of frailty for older people and individuals in their middle age.

 

Acknowledgements: The authors thank all participants for their cooperation and the Chilean Health Ministry and Department of Public Health, The Pontificia Universidad Católica de Chile for commissioning, designing, and conducting the second National Health Survey 20016–2017.

Financial support: The Chilean National Health Survey (CNHS) 2016–2017 was funded by the Chilean Ministry of Health and led by the Department of Public Health, The Pontificia Universidad Católica de Chile. The present study was funded by the Chilean Health Ministry as part of the Third health surveillance in Chile. The funders had no role in study design, data collection, data analysis, data interpretation or any decision related to this manuscript.

Conflict of interest: None.

Authorship: F.D generated the research question. F.D, F.P.-R. and C.C.-M. planned the analysis. F.D. performed the literature search. F.D performed the analysis with support from C.C-M and F.P-R. F.D wrote the first draft of the manuscript. All authors critically reviewed this and previous drafts. All authors approved the final draft for submission. F.P-R. is the guarantor.

Ethical standards: The CNHS 2016–2017 was funded by the Chilean Ministry of Health and approved by the Ethics Research Committee of the School of Medicine at the Pontificia Universidad Católica de Chile (No. 16–019).

 

References

1. Walston J, Hadley EC, Ferrucci L, Guralnik JM, Newman AB, Studenski SA, et al. Research Agenda for Frailty in Older Adults: Toward a Better Understanding of Physiology and Etiology: Summary from the American Geriatrics Society/National Institute on Aging Research Conference on Frailty in Older Adults: Research agenda for frailty. J Am Geriatr Soc. 2006 Jun;54(6):991–1001. doi: 10.1111/j.1532-5415.2006.00745.x.
2. Collard RM, Boter H, Schoevers RA, Oude Voshaar RC. Prevalence of Frailty in Community-Dwelling Older Persons: A Systematic Review. J Am Geriatr Soc. 2012 Aug;60(8):1487–92. doi: 10.1111/j.1532-5415.2012.04054.x.
3. Clegg A, Young J, Iliffe S, Rikkert MO, Rockwood K. Frailty in elderly people. The Lancet. 2013 Mar;381(9868):752–62. doi: 10.1016/S0140-6736(12)62167-9
4. Buckinx F, Rolland Y, Reginster JY, Ricour C, Petermans J, Bruyère O. Burden of frailty in the elderly population: perspectives for a public health challenge. Arch Public Health. 2015 Dec;73(1):19. doi: 10.1186/s13690-015-0068-x.
5. Buta BJ, Walston JD, Godino JG, Park M, Kalyani RR, Xue QL, et al. Frailty assessment instruments: Systematic characterization of the uses and contexts of highly-cited instruments. Ageing Res Rev. 2016 Mar;26:53–61. doi: 10.1016/j. arr.2015.12.003.
6. Mitnitski AB, Mogilner AJ, Rockwood K. Accumulation of Deficits as a Proxy Measure of Aging. Sci World J. 2001;1:323–36. doi: 10.1100/tsw.2001.58.
7. Kojima G, Iliffe S, Walters K. Frailty index as a predictor of mortality: a systematic review and meta-analysis. Age Ageing. 2018 Mar 1;47(2):193–200. doi: 10.1093/ageing/afx162.
8. Kane AE, Howlett SE. Sex differences in frailty: Comparisons between humans and preclinical models. Mech Ageing Dev. 2021 Sep;198:111546. doi:10.1016/j.mad.2021.111546.
9. Gordon E, Hubbard R. Physiological basis for sex differences in frailty. Curr Opin Physiol. 2018 Dec;6:10–5. doi: 10.1016/j.exger.2016.12.021.
10. Kirkwood TBL. Understanding the Odd Science of Aging. Cell. 2005 Feb;120(4):437–47. doi: 10.1016/j.cell.2005.01.027.
11. Wilson D, Jackson T, Sapey E, Lord JM. Frailty and sarcopenia: The potential role of an aged immune system. Ageing Res Rev. 2017 Jul;36:1–10. doi: 10.1016/j.arr.2017.01.006.
12. Sezgin D, Liew A, O’Donovan MR, O’Caoimh R. Pre-frailty as a multi-dimensional construct: A systematic review of definitions in the scientific literature. Geriatr Nur (Lond). 2020 Mar;41(2):139–46. doi: 10.1016/j.gerinurse.2019.08.004
13. Hanlon P, Nicholl BI, Jani BD, Lee D, McQueenie R, Mair FS. Frailty and pre-frailty in middle-aged and older adults and its association with multimorbidity and mortality:a prospective analysis of 493 737 UK Biobank participants. Lancet Public Health. 2018 Jul;3(7):e323–32. doi: 10.1016/S2468-2667(18)30091-4.
14. Petermann-Rocha F, Martínez-Sanguinetti MA, Leiva-Ordoñez AM, Celis-Morales C. Carga global de morbilidad y mortalidad atribuible a factores de riesgo entre los años 1990 y 2019: ¿Cuál es la realidad chilena? Rev Médica Chile. 2021 Mar;149(3):484–6. http://dx.doi.org/10.4067/s0034-98872021000300484
15. Aranco N, Stampini M, Ibarrarán P, Medellín N. Panorama de envejecimiento y dependencia en América Latina y el Caribe [Internet]. Inter-American Development Bank; 2018 Jan. doi.org/10.18235/0000984
16. United NAtions Economic Commission for Latin America and the Caribbean. Latin America and the Caribbean demographic observatory 2019:: population projections. S.l.: UNITED NATIONS; 2022.
17. Troncoso-Pantoja C, Concha-Cisternas Y, Leiva-Ordoñez AM, Martínez-Sanguinetti MA, Petermann-Rocha F, Díaz-Martínez X, et al. Prevalencia de fragilidad en personas mayores de Chile: resultados de la Encuesta Nacional de Salud 2016-2017. Rev Médica Chile. 2020 Oct;148(10):1418–26. doi.org/10.4067/S0034-98872020001001418
18. Albala C, Lera L, Sanchez H, Angel B, Márquez C, Arroyo P, et al. Frequency of frailty and its association with cognitive status and survival in older Chileans. Clin Interv Aging. 2017 Jun;Volume 12:995–1001. doi: 10.2147/CIA.S136906.
19. MINSAL. Encuesta Nacional de Salud 2016-2017. Chile: Ministerio de Salud; 2017
20. Leng S, Chen X, Mao G. Frailty syndrome: an overview. Clin Interv Aging. 2014 Mar;433. doi: 10.2147/CIA.S45300.
21. Rockwood K. A global clinical measure of fitness and frailty in elderly people. Can Med Assoc J. 2005 Aug 30;173(5):489–95. doi: 10.1503/cmaj.050051.
22. Searle SD, Mitnitski A, Gahbauer EA, Gill TM, Rockwood K. A standard procedure for creating a frailty index. BMC Geriatr. 2008 Dec;8(1):24. doi: 10.1186/1471-2318-8-24.
23. Rockwood K, Mitnitski A. Frailty in Relation to the Accumulation of Deficits. J Gerontol A Biol Sci Med Sci. 2007 Jul 1;62(7):722–7. doi: 10.1093/gerona/62.7.722.
24. Williams DM, Jylhävä J, Pedersen NL, Hägg S. A Frailty Index for UK Biobank Participants. J Gerontol Ser A. 2019 Mar 14;74(4):582–7. doi: 10.1093/gerona/gly094.
25. Khadka J, Visvanathan R, Theou O, Moldovan M, Amare AT, Lang C, et al. Development and validation of a frailty index based on Australian Aged Care Assessment Program data. Med J Aust. 2020 Oct;213(7):321–6. doi: 10.5694/mja2.50720
26. Hoogendijk EO, Theou O, Rockwood K, Onwuteaka-Philipsen BD, Deeg DJH, Huisman M. Development and validation of a frailty index in the Longitudinal Aging Study Amsterdam. Aging Clin Exp Res. 2017 Oct;29(5):927–33. doi: 10.1007/s40520-016-0689-0.
27. Fried LP, Ferrucci L, Darer J, Williamson JD, Anderson G. Untangling the Concepts of Disability, Frailty, and Comorbidity: Implications for Improved Targeting and Care. J Gerontol A Biol Sci Med Sci. 2004 Mar 1;59(3):M255–63. doi: 10.1093/gerona/59.3.m255.
28. O’Caoimh R, Sezgin D, O’Donovan MR, Molloy DW, Clegg A, Rockwood K, et al. Prevalence of frailty in 62 countries across the world: a systematic review and meta-analysis of population-level studies. Age Ageing. 2021 Jan 8;50(1):96–104. doi: 10.1093/ageing/afaa219.
29. Coelho-Junior HJ, Marzetti E, Picca A, Calvani R, Cesari M, Uchida MC. Prevalence of Prefrailty and Frailty in South America: A Systematic Review of Observational Studies. J Frailty Aging. 2020;9(4):197-213. doi: 10.14283/jfa.2020.22.
30. Poli S. Frailty is associated with socioeconomic and lifestyle factors in communitydwelling older subjects. Aging Clin Exp Res. :8. doi: 10.1007/s40520-016-0623-5.

© Serdi 2023